Violet-tailed Sylph Aglaiocercus coelestis Scientific name definitions

Although formerly considered a subspecies of Long-tailed Sylph (Aglaiocercus kingi), the morphology, behavior, range, and altitudinal distribution of Violet-tailed Sylph classify it as its own species. It is common in cloud forests, especially in mossy areas and around 1000 meters in elevation; these sylphs also makes use of forest borders and partly open areas with shrubs and trees. The stunningly long outermost tail feathers of the male are purple with blue tips, distinguishing the male from the similar Long-tailed Sylph (Aglaiocercus kingi) which has a blue or teal tail in the area of range overlap. Violet-taileds usually forage near the ground, making repeated circuits to the flowers on vines, trees, or shrubs distantly spaced from one another. Some altitudinal migration occurs based on the flowering time of plants. They also gather insects from plants or by aerial hawking. A cursory observation might mislead one to believe that Violet-tailed Hummingbirds breed year-round, but they actually build nests outside of the breeding period (October-February) for the purpose of roosting.

Male 18–21 cm (including outer tail feathers 10–15 cm), female 9·5–9·7 cm; 4·6–5·2 g. Male has short, straight, black bill; crown and back shining green becoming violet-blue on rump , small postocular spot buffy white; gorget violet-blue, rest of underparts green; tail elongated , deeply forked, mostly iridescent metallic violet , tipped blue . Female has crown glittering blue, postocular spot whitish ; throat white with green spots, band across chest white, rest of underparts cinnamon-rufous; tail short, unforked, bluish green, with outer rectrices tipped white. Juvenile dull green above, buffy green below, head feathers with buffy fringes. In race aethereus, male has gorget green, female less heavily spotted on throat.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Cloudforest, forest borders, semi-open terrain with shrubs and stands of trees, at 1000–2000 m, occasionally much lower, most numerous around 1000 m. Forages from near ground occasionally up to treetops, along edges and trails and inside forest. Male and female trap-line along clumps of dispersed flowers; male occasionally defends feeding territory.

Sedentary, with some local altitudinal dispersal depending on flowering season. At La Planada Reserve, Nariño (SW Colombia), in zone of contact with A. kingii, present species is dominant in dry season, Jan–Apr, numbers declining during wet season.

Nectar of flowering vines, shrubs and trees, including Bomarea, Clusia, ericads, bromeliads and Inga. Often clings to corolla while feeding. Insects are caught in the air by hawking, or gleaned from vegetation.

Presumed song a continuous series of short notes, “psit..psit..psit..”, at a rate of c. 2 notes/second. Calls include a repeated, short, buzzy single or double “bzzt” or “bz-zzrt”, and a higher-pitched drawn-out “bzeee”. Also a high-pitched falling/rising twittering “seee..seee..seee..seee..tr-tr-tititi-teetsee..see..see”, possibly a chasing call, somewhat similar to Adelomyia melanogenys.

Oct–Feb. Domed nest with side entrance is built from moss and spider webs in clumps of moss or epiphytes. Clutch two white eggs; incubation 15–17 days, by female; chick pale-coloured with sparse greyish dorsal down; fledging at 26–30 days. Male and female build nests outside the reproductive period where they roost at night; this may have misled ornithologists to assume breeding activity almost year-round.

Not globally threatened (Least Concern). Common resident of cloudforest. The species will tolerate areas of man-made habitats as long as patches of forest remain. Several national parks within the distributional range of the species provide adequate protection for local populations. In Colombia, common resident at edges of cloudforest of Los Farallones National Park, near Cali, with local densities of at least 3–4 pairs/km²; at La Planada Reserve, density varies from at least 5–7 pairs/km² in dry season to at least 2 pairs/km² in wet season; also recorded in Río Ñambi Reserve.